Intrinsic charge polarization in Bi₁₉S₂₇Cl₃ nanorods promotes selective C—C coupling reaction during photoreduction of CO₂ to ethanol

Abstract

Obtaining multi-carbon products via CO₂ photoreduction is a major catalytic challenge involving multielectron-mediated C—C bond formation. Complex design of multicomponent interfaces that are exploited to achieve this chemical transformation, often leads to untraceable deleterious changes in the interfacial chemical environment affecting CO₂ conversion efficiency and product selectivity. Alternatively, robust metal centers having asymmetric charge distribution can effectuate C—C coupling reaction through the stabilization of intermediates, for desired product selectivity. However, generating inherent charge distribution in a single component catalyst is a difficult material design challenge. Here, a novel photocatalyst, Bi₁₉S₂₇Cl₃, is presented which selectively converts CO₂ to a C₂ product, ethanol, in high yield under visible light irradiation. Structural analysis through transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy reveals the presence of charge polarized bismuth centers in Bi₁₉S₂₇Cl₃. The intrinsic electric field induced by charge polarized bismuth centers renders better separation efficiency of photogenerated electron–hole pair. Furthermore, charge polarized centers yield better adsorption of CO* intermediate and accelerate the rate determining C—C coupling step through the formation of OCCOH intermediate. Formation of these intermediates is experimentally mapped by in situ Fourier-transform infrared spectroscopy and further confirmed by theoretical calculation.